1. Field of the Invention
The present invention relates to a liquid crystal display that is of a transmissive type or of a transreflective type liquid crystal display equipped with LEDs (light emitting diodes) as a backlight, and a backlight control device for the liquid crystal display for controlling the amount of light emission of the LEDs.
2. Description of the Related Art
Conventionally known liquid crystal displays include a transmissive type liquid crystal display having a liquid crystal device and a backlight such as a fluorescent lamp, LEDs or the like are disposed at the back of the liquid crystal device, which displays through irradiating light from behind the liquid crystal device. Other known liquid crystal displays include a reflective type liquid crystal device which displays through reflecting light such as natural light, room light or the like and a transreflective (half-transmissive) type liquid crystal display which displays through the use of a transmissive type in combination with a reflective type.
In this manner, transmissive type and transreflective type liquid crystal displays use for example an LED as a backlight. When the liquid crystal display is used, a drive current is applied to the LED without regard to the brightness around the liquid crystal panel to drive the LED.
For this reason, when the surrounding area of the panel is bright, the current applied to the LED may be more than necessary, which deteriorates the viewability of the liquid crystal panel. Moreover, when a battery is used as a driving power supply for the LED, there is a problem in that the battery quickly discharges.
In the meantime, conventionally, a drive current is applied to the LED without regard to the ambient temperature around the liquid crystal panel to drive the LED.
However, when the ambient temperature around the liquid crystal panel changes, the temperature of the LED changes accordingly. For this reason, the luminance factor of the LED changes due to the change in the temperature of the LED in use, and therefore the LED cannot achieve an optimum luminance factor. As a result, there is a problem in that the energy of the power supply source such as the battery cannot be effectively utilized.
Moreover, when multiple LEDs are used and driven, and if the LEDs are simultaneously turned on, the drive peak current value becomes large. When the input power supply source is the battery, there is a problem in that the input voltage lowers according to the impedance of the battery, and the efficiency of the power supply section deteriorates.
Accordingly, in view of the problems discussed above, it is a first advantage of the present invention to provide backlight control device for a liquid crystal display in which, when a battery is used as the power supply source for the LED, upon using the liquid crystal display, the power consumption of the battery can be reduced, and the display quality of the liquid crystal panel can be improved.
Also, it is a second advantage of the present invention to provide a backlight control device for a liquid crystal display in which the power supply source for the LED can be used in an energy efficient manner upon using the liquid crystal display, and the display quality of the liquid crystal panel can be improved.
Furthermore, it is a third advantage of the present invention to provide a backlight control device for a liquid crystal display in which upon using the liquid crystal display, the display quality of the liquid crystal panel can be improved regardless of the differences in the brightness in the surroundings and differences in the ambient temperature.